(1) Field of the Invention
The present invention relates to a technology for preventing unauthorized use of a recording medium which is mountable to a terminal device.
(2) Description of the Related Art
In recent years, a system has been proposed that enables users to access information recorded on a recording medium with use of a terminal device to which the recording medium is mountable, such as a portable telephone.
JP 2001-134688 is a reference which discloses a system that includes a smartcard and a portable terminal device. Here, the smart card stores thereon user information and information relating to applications to be used, and the portable terminal device is equipped with an authentication unit that authenticates whether the user is authorized to use the portable terminal device.
In this system, when the smart card is mounted to the portable terminal device, authentication is performed to determine whether the user is the authorized user, with use of information inputted through the portable terminal device and information that is on the smart card. When the user is authenticated as the authorized user, the user will be allowed to access information written on the smart card.
However, with the aforementioned technology, the authentication unit within the portable terminal device is not protected against an unauthorized external attack. Therefore, there is a possibility that a malicious third party decodes the authentication unit of the portable terminal, and changes the authentication unit to always authenticate the third party to be the authorized user. Such tampering will allow third parties to access the information recorded on the recording medium.